Descrizione del progetto
Il ruolo dell’altezza nella risposta di un albero alla siccità
Gli alberi si adattano alle condizioni di siccità riducendo la traspirazione delle foglie e, a sua volta, il flusso di linfa, prevenendo perdite d’acqua ed embolie estese. Gli alberi alti sono più sensibili allo stress da siccità, ma i meccanismi che provocano questa maggiore vulnerabilità non sono ancora del tutto chiari. Il progetto DISTRESS mira a considerare la legge del flusso dei fluidi di Darcy per determinare l’influenza dell’altezza degli alberi sulle risposte a breve e lungo termine alla siccità. Attraverso l’analisi dei diversi tratti degli alberi tropicali e dei dati sul flusso di linfa di 159 specie di diversi biomi, DISTRESS porterà a una più profonda comprensione della vulnerabilità degli alberi alla siccità e contribuirà a simulazioni migliori degli effetti dei cambiamenti climatici sugli ecosistemi forestali.
Obiettivo
Plants adjust leaf water potential and hydraulic conductance under drought through stomatal behaviour, reducing sap flow and protecting plants from extensive water loss and embolism. Due to the negative effect that vapour pressure deficit (VPD) and tree height have on canopy-scale water conductance (G), Darcy’s law predicts a decline in G due to the expected increase in VPD following climate warming, to which tall trees would be presumably more sensitive. Further work is thus needed to understand the effect that tree size has on tree response to increased VPD and drought. This project aims at (1) testing whether, at a given VPD, trees adjust different functional traits to compensate for the negative effect of height on G in (a) tropical forests and (b) at a global scale, and (2) describing the mechanisms behind these adjustments and the potential interactions with other functional processes that may impair tree response to drought stress with increasing size. We will first measure multiple functional traits (including sap flux, gas exchange and leaf and xylem water potential) on trees of different heights to test Darcy’s law predictions and evaluate the role that the trade-offs among traits play on enhanced vulnerability to drought with increasing tree size in tropical forests. In order to assess whether the studied mechanisms prevail across species and ecosystems, we will perform a global-scale analysis of sap-flow and, thus, G responses to VPD as a function of tree height using the sap-flux data from 159 species and nine different biomes gathered within SAPFLUXNET. This integrated analysis will provide a better understanding of the role that tree size plays in tree vulnerability to drought in the short (temporary physiological response) and long term (legacy effects), allowing the improvement of mechanistic models of tree response to climatic variability. Such information is essential to better simulate the impact that climate change may have on forest ecosystems.
Campo scientifico
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Meccanismo di finanziamento
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinatore
08193 Bellaterra
Spagna